There are two main types of preterm births: "indicated" preterm births and "spontaneous" preterm births. Indicated preterm deliveries are those deliveries that your provider initiates prior to 37 weeks because of medical or obstetrical problems that place you and your baby at risk.

Indicated preterm births account for 1/3 of all preterm births and can be caused by things like preeclampsia (toxemia), diabetes, fetal growth problems, or placental bleeding. In these pregnancies, your provider must weigh the risk of prematurity for the baby versus the risk to you and the baby of continuing the pregnancy.

Spontaneous preterm deliveries occur in an otherwise healthy pregnancy and are due to either preterm rupture of the amniotic fluid or to the unexpected onset of preterm labor.